By manipulating lightningchakra into their hand, the user can make the lightning expand to create the form of a hound. The hound remains connected to the user's hand, allowing them to control it during its attack.

Trivia

Raijū is a mythological creature in Shintō religion, companion to the Shintō god of lighting, Raijin. Raijū has many common representations, with a white and blue wolf sometimes engulfed in lightning being among them, akin to the form Kakashi's technique takes.